Under some circumstances, the secure sealing of containers is necessary. It is of particular importance if such containers hold dangerous substances, such as fissile materials.
For example, an inspection agency wishes to verify that a cask (container) containing nuclear spent fuel is transferred between two facilities without being opened. Transport casks are filled at a facility, transferred by truck, rail or boat to another facility and then re-opened.
The inspector traditionally has access to the casks and lids at three different stages—before they are filled, during transfer and after the cask is opened and emptied.
It is desirable that casks be filled under surveillance, closed by the operator and sealed by the operator, but no inspector from the agency is required to be present during the filling/closing/sealing operation. The seal applied by the operator must be conceived in a way to (i) avoid intentional/unintentional bad installation that will inhibit/alter the correct function of the seal, (ii) uniquely match cask and lid, (iii) detect an unauthorized opening during transport, (iv) avoid being cloned, and (v) store data and guarantee that the data has not been manipulated.
Techniques for secure sealing of containers are known, i.e. sealing whereby tampering/opening of the container thereafter is detectable/visible.
Known ways of sealing nuclear containers make use of perforated bolts or other fixtures in combination with wire seals (metal cable or fibre optic loops). All the known systems require the presence of a trusted person (i.e. an inspector) at the time of closing and opening.
For example, prior solutions involve the use of passive loop seals (like the COBRA seal) or active electronic seals (like EOSS). In each case, a wire or fibre optic is passed through a fixture in the cask and in the lid when the cask is closed. The wire is connected to a seal. In case of the COBRA seal, to open the cask the seal must be broken. In case of the EOSS seal, openings are recorded internally in the seal. A disadvantage is that both previous systems rely on the correct wire installation on the fixtures on the cask. Also, a loose wire may allow the opening of the cask without detection by the seal. Further, the fibre optic wire may be damaged during transport, rendering the seal useless. The COBRA system requires an inspection before the cask is opened (seal broken) because there is no way to determine the time at which the seal was broken.
Other seals detect displacement by means of contact or magnets, but the methods are not very strong against tampering attempts.
Even if the existing sealing bolts already seal the containers very securely, there is no known system that fulfils all the requirements, especially the possibility to work unattended without compromising the security of the system.
US-A-2004/239435 is generally directed to a tamper detection system for life raft containers. The life raft container is used for storing an inflatable life raft and includes a top part and a bottom part that are placed directly onto one another. The container further comprises an RFID system capable of detecting when the container has been opened, i.e. when a distance between the container parts has increased. Specifically, a mother RFID tag and daughter RFID tag are linked to one another and actively communicate with one another to determine a distance between them. When the distance between the mother RFID tag and the daughter RFID tag increases or decreases with respect to a distance D beyond a predetermined amount.
WO-A-2005/111961 is generally directed to the use of RFID tags for tamper-evidence. Specifically, a pair of RFID tags is used to detect a change in the relative position of a closure lid with respect to a container.
WO-A-2014/009981 is generally directed to the synchronization of a real-time Ultra-Wide Band locating system. Specifically, triangulation in three dimensions using at least four readers is used to determine the 3D position of a tagged item.